This invention relates to sampling effluent gas for contaminants and in particular to an apparatus and method capable of continuous sampling of effluent-bearing gas for the presence of contaminants.
A common practice to obtain an indication of the amount of contaminant in a gas is to pass a given volume of the gas through a given volume of liquid and subsequently determine, by chemical analysis, the amount of contaminant collected in the liquid. However, this practice is not always satisfactory because the value obtained on analysis represents only an average value for the period in which the gas was passed through the liquid. Such an average value may appear satisfactory when in reality the average contamination -- over a longer period -- is higher. For example, if in the sampling time period for which the gas is passed through the liquid, the contaminant level is substantially negligible, a low reading will be obtained. But if in a very short period thereafter the contaminant level becomes very high, the previous reading is obsolete -- or at the least misleading. Also, there is nothing to relate the sampling period with industrial activity.
This prior art method has the additional disadvantage that often there can be a considerable delay between the time the sample is taken and the time when it is analyzed. This last disadvantage can have very serious consequences. For instance, in an industrial operation which has an effluent cleaning or processing system, it is imperative to know when the system is operating satisfactorily. If samples are taken, and analyzed later, and the effluent cleaning system has in the meantime broken down, considerable undesirable pollutants or contaminants may have escaped into the atmosphere. The present invention has overcome all of these disadvantages by being capable of continuously monitoring stack emissions and giving an almost instantaneous analysis of pollutants therein.